Military

Further Reading

X-50 Dragonfly Canard Rotor/Wing (CRW)

The Army, Navy and Marine Corps have a need for affordable, survivable, vertical take-off and landing (VTOL) air vehicles to support dispersed units in littoral and urban areas. The Canard Rotor/Wing (CRW) program explores innovative VTOL technologies and concepts with the potential for significant performance improvements that would satisfy stressing mission needs. One such concept is the advanced Canard Rotor/Wing (CRW) aircraft, that offers the potential for a high speed rapid response capability from a VTOL unmanned air vehicle with significant range and stealth improvements as compared to other VTOL concepts. Design and fabrication of this scaled vehicle concept will validate the command and control, stability and control system and aerodynamic performance required for vertical take-off, landing and hover via a rotating center wing that stops and locks in place for efficient high speed cruise.

An operational CRW UAV would be able to take off and land in confined areas without a launch or recovery system, rapidly transition to and from a fixed wing mode and fly at speeds in access of 375 knots. The flexibility achieved through these various flight modes, combined with the high-speed performance and survivability of this revolutionary new concept makes the CRW an exciting option for manned and unmanned applications.

Boeing has leveraged specific expertise that was developed during the company's previous work on reaction drive rotor systems, including both the XH-17 in the early 1950s and the XV-9A in the mid-1960s. The Boeing patented CRW concept is an outgrowth from these previous activities.

In response to a Navy requirement for an unmanned, high-speed, ship-based vertical take off and landing (VTOL), McDonnell Douglas Helicopter developed a concept called Canard-Rotor-Wing (CRW). The CRW is a stoppable-rotor design which can hover and fly at low-speeds like a conventional helicopter, whereas in its stopped-rotor mode it can fly at high speeds comparable to those of fixed-wing aircraft. Initial concepts include a land- or ship-based medium-range vertical takeoff and landing, remotely piloted vehicle. An operational CRW UAV would be able to take off and land in confined areas without a launch or recovery system, rapidly transition to and from a fixed wing mode and fly at speeds in access of 375 knots.

The CRW is propelled in both rotary-wing and fixed-wing modes using a conventional turbofan engine. A diverter valve directs the exhaust gas produced by the engine either to the rotor or aft to the jet thrust nozzle, or to both during transition. A two-bladed teetering rotor is used to generate the required lift for hover and low-speed forward flight. The CRW would spin a center wing to take off like a helicopter.The vehicle would then accelerate to about 120 knots when flaps would deploy from the front and rear wings. Once the rotorcraft is at a sufficient forward velocity, the required lift generation is transferred from the rotor to a canard and horizontal tail. Flap deployment would off load the spinning center wing, which could then stop rotation and be locked into a position across the fuselage to perform as a third wing. The flaps on the other two wings would then be retraced and all three wings would share the lift loads in a fixed wing flight mode. A reverse of these events would transition the CRW back to its rotary wing--VTOL mode for landing on small landing areas.

By using a reaction-drive rotor system, the CRW concept eliminates the need for a mechanical drive train and transmission, as well as the need for an anti-torque system. Eliminating these typically heavy, maintenance-intensive systems will greatly reduce vehicle weight, maintenance, complexity, and cost. Because the CRW's rotor is stopped to allow high-speed forward flight, the rotor's airfoil cross section must be elliptical. This is a compromise between the optimum airfoil shape for conventional rotor flight and that for high-speed stopped-rotor flight.

Possible manned and unmanned missions for such a vehicle include reconnaissance, communications and data relay, logistics re-supply, urban operations and delivery of both lethal and non-lethal munitions. The Navy and Marine Corps have expressed a strong interest in the CRW concept for both tactical UAV applications requiring VTOL operations from small-deck ships and manned applications such as a V-22 Osprey escort. They have funded a portion of the research activities to date and are considering transitioning this technology into a UAV engineering, manufacturing, and development phase following its successful flight demonstration.

In June 1998 a $24 million agreement between the Defense Advanced Research Projects Agency (DARPA) and The Boeing Company funded a 37 month effort by the Boeing Phantom Works to design, build and fly two technology demonstrators to assess and validate this advanced rotorcraft. DARPA and Boeing agreed to a 50/50 cost share agreement to validate this revolutionary concept in a joint advanced technology demonstration program known as "Dragonfly". Each contributed $12 million toward the program, initially planned to lead to flight demonstration in early 2001.

Development of the technology demonstrators is being conducted by Phantom Works personnel in Mesa, Ariz., St. Louis, Mo., as well as several other Boeing facilities. Final assembly is now under way at the Mesa facility, with a first flight expected in 2002.

On 04 December 2003 the Boeing Company's Canard Rotor/Wing (CRW) concept demonstrator completed its first hover flight at the U.S. Army Proving Ground in Yuma, Ariz. During the flight test, the CRW advanced technology demonstrator - known as the X-50A Dragonfly - flew for about 80 seconds at 8:10 a.m. MST. It lifted off vertically from the launch site to an altitude of 12 feet above the ground, hovered and then vertically landed, commencing the flight test program.

The unmanned X-50A CRW has a length of 17.7 feet and is 6.5 feet high. The rotor blades have a diameter of 12 feet. Powered by a conventional turbofan engine, the X- 50A will utilize diverter valves to direct thrust to the rotor blade tips (for helicopter mode), or aft to the jet nozzle (for fixed wing mode). Dual bleed thrust will be used during transition. By directing thrust through the rotor tips, the CRW concept eliminates the need for a heavy and complex mechanical drive train, transmission and anti-torque system. The CRW will be much lighter and simpler than traditional rotorcraft and will therefore be much cheaper to operate and support.

Aviation enthusiasts may have noticed that the X-50 designation was not the next in line. But Boeing's X-50 program manager Steve Bass said that Boeing got the number out of sequence by special request because the X-50 designation is so fitting for the CRW concept - 50 percent helicopter and 50 percent airplane.